There are just things we wanted to do but we can't, no matter how we try. But nobody said we can't do it the way we wanted to. And if somebody does tell you that you can't do it right, then show that person how to do it better. (Okay, did I just said that?)
And if in the process of doing, you made mistakes, then I guess it's time to take the alternative route - if plan A did not work, try plan B. You can try to complete the alphabet. And then at least, you found other ways not to do it the way you did. Mistakes are actually a source of inspiration, don't you think? As for me, it does motivate me to become better at something, for something and in something. Whatever they are, that is.